1. Field of the Invention
The invention relates generally to methods and apparatus for identification and optimization of coating materials and properties for desired applications. More specifically, the invention relates to an improved process of creating coatings, involving identifying candidate materials and screening and optimizing formulations and coating parameters for desired applications, for example the measurement of the moisture barrier properties of films.
2. General Background and State of the Art
Development of coating materials, for example adhesive coatings, release coats, protective coatings, and the like as well as films and laminate constructions of layered materials, has conventionally been a time consuming and labor intensive process. Candidate materials are identified primarily based on knowledge and experience with what compositions have worked before in related applications and investigating like materials and combinations of materials. This usually involves preparing a coating formulation, preparing a test coating for evaluation (often involving several tries to attain the desired parameters such as coat weight, cure, etc. for evaluation), drying the coating, then evaluating the coating by testing the property of interest, such as permeability, tack, shear, bending strength, surface roughness, etc., and entering the results in a database for comparison with further coatings to be developed and tested. Problems of cross-contamination and holdover further limit the number of formulations that can be screened in a given time period. This is a time-consuming process and as a result one skilled in the art, even with support staff to assist and carry on tasks in parallel, has conventionally been able to screen at most a few coatings per day, most often only one or two.
Because of the lengthy time required to screen and then investigate candidate materials and associated coating application parameter values to select and optimize coatings, those skilled in the art generally must focus on families of materials known to possess properties likely to prove successful in the intended use. Investigation of unconventional or simply previously untried materials is usually limited. Moreover, development of coating materials for a particular application is also a time-consuming process, and development of new coatings, while potentially beneficial, sometimes cannot be pursued due to economic considerations arising out of the time and effort involved.
Requisite in the development of new coating materials is the use of a particular coating method as well as consideration of holdover or carryover effects. Holdover effects result in the contamination of one candidate coating material due to residual coating material remaining in the coat dispensing apparatus and/or coat-receiving substrate from a prior test coating material. Contaminations as a result of holdover effects are generally additive and provide a level of error in coat formulation that is difficult to control. It is therefore preferable, especially when the volume of coating material to be tested is small, to use a coating method that either eliminates or significantly reduces holdover effects. Use of a disposable method for dispensing as well as receiving the test coat material would eliminate problems associated with holdover effects.
A variety of methods for coating desired substrates or materials are available and include spin coating, die coating and non-contact jet coating methods. Spin coating is a technique commonly used in the field of electronics where the coat material is dispensed onto a spinning plate where it is spread by centrifugal force. The coatweights resulting from this method are limited to very thin coatings and there is a significant loss of material during the coating process. In both the die coating and non-contact jet coating methods, die and jetting nozzle costs prohibit their modification to disposable units. Prior to the instant application, an inexpensive, efficient and disposable method for testing a large number of coating materials has not been known. While many significant advances in coating technology have been made in recent years, acceleration of the rate at which coating materials can be identified, screened, investigated and optimized will be recognized as a desirable goal by those skilled in the art.